[media] v4l: Add v4l2 subdev driver for S5K6AAFX sensor

This driver exposes preview mode operation of the S5K6AAFX sensor with
embedded SoC ISP. The native capture (snapshot) operation mode is not
supported.
Following controls are available:
 manual/auto exposure and gain, power line frequency (anti-flicker),
 saturation, sharpness, brightness, contrast, white balance temperature,
 color effects, horizontal/vertical image flip, frame interval,
 auto white balance.
RGB component gains are currently exposed through private controls.

Reviewed-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>